Industrial furnace

ABSTRACT

An industrial furnace for heating metal plate and the like with flames directed at the horizontally disposed plate from above and below by suitably mounted jets. The lower jets are raised above the furnace floor and when operated in a turned-down or low heat output mode discharge the fuel gas and/or flame at a speed greater than the free-fall speed of scale and the like dropping from the plates to prevent a clogging of the burners. The floor burners are further provided with vertically extending gas discharge pipes which terminate in scale collection containers so that scale dropping into the burners when the burners are turned off falls through the operative burner portions for collection and subsequent removal without obstructing the burner.

United States Patent 91 Bunzel et al.

[ Dec. 25, 1973 INDUSTRIAL FURNACE [75] Inventors: Eckard Bunzel, Neuss; Robert Spessert, Bergisch-Gladbach; Karl Rieskamp, Mulheim/Ruhr; Willi Hildebrand, Dinslaken-Hiesfeld, all I of Germany [73] Assignee: OFU'Ofenbau-Union Gmbll,

Duesseldorf, Germany [22] Filed: Aug. 13, 1971 [21] Appl. No.: 171,675

[30] Foreign Application Priority Data Aug. 17, 1970 Germany P 20 40 766.3

[52] US. Cl. 432/126, 432/2 [51] Int. Cl. 9 F27b 9/14 [58] Field of Search 263/6 B, 6 R; 431/9;

[56] References Cited UNITED STATES PATENTS l-lorn 263/6 R Kereluk 263/6 R Boelsma 431/9 X Primary Examiner-Meyer Perlin Assistant Examinerl-larold Joyce Att0rney-T0wnsend and Townsend [5 7 ABSTRACT An industrial furnace for heating metal plate and the like with flames directed at the horizontally disposed plate from above and below by suitably mounted jets. The lower jets are raised above the furnace floor and when operated in a turned-down or low heat output mode discharge the fuel gas and/or flame at a speed greater than the free-fall speed of scale and the like dropping from the plates to prevent a clogging of the burners. The floor burners are further provided with vertically extending gas discharge pipes which terminate in scale collection containers so that scale dropping into the burners when the burners are turned off falls through the operative burner portions for collection and subsequent removal without obstructing the burner.

9 Claims, 2 Drawing Figures mm Em 3.781; 166

SHEET 10F 2 lure/71ers ECKARD BUNZEL ROBERT SPESSERT KARL RIESKAMP WI Ll HINDEBRANDT ATTORNEYS T PA'IEHTEU[K172515913 3.781.166

SHCET 2 OF 2 Myanmar ECKARD BUNZEL ROBERT SPESSERT KARL RIESKAMP WILLI HINDEBRANDT ATTORNEYS INDUSTRIAL FURNACE BACKGROUND OF THE INVENTION This invention relates to industrial furnaces having heating chambers in which the material to be heated is conveyed in a generally horizontal plane spaced from both the ceiling and the floor. Upper heating means, preferably a plurality of burners are distributed over the width and length of the furnace roof and discharge a downwardly directed fuel jet for combustion above the plate.

Such furnaces per se are known and have a relatively high capacity since the plates can be conveyed through the heating space of the furnace while in a horizontal position. The capacity can be further increased by conveying the plates through the furnace at a more rapid rate. This, however, necessitates l a correspondingly longer heating space. Industrial furnaces having increasingly large hearth areas. and heating spaces often give rise to a non-uniform heating of the material. Even with burners arranged in the furnace ceiling satisfactory results cannot be obtained since the burners only heat the upper side of the plate as the plate moves through the furnace. The lower side of the plate is not contacted by the flame and is. heated by heat transmission through the plate. Its temperature, therefore, varies substantially from the temperature of the upper plate side which is contacted by the flame.

Another prior art furnace of the general type discussed above transports the material to be'heated in an upright, vertically standing position through the furnace past burners positioned on both sides of the material and mounted to the furnace ceiling. To the extend necessary additional burners are provided in the furnace floor which direct flame in a generally upward direction. The aforementioned problems of non-uniform heating do not exist in this furnace because the material is subjected to direct heat or flame on both sides thereof. There is, furthermore, no substantial problem of plugging the burners in the furnace bottom with falling scale from the material since the material is supported on its narrow side, stands upright and, therefore, produces little scale and since the material is conveyed through the furnace in the space between adjacent bottom burners so that falling scale collects between and not on top of the bottom burners. However, the transport of plates in an upright position, particularly when heated is difficult and can result in a deformation of the plates, buckling, warping or the like.

SUMMARY OF THE INVENTION The present invention provides an industrial furnace for heating large objects such as flat plate and the like in which the plate is conveyed through the furnace in a fully supported, essentially horizontal position and in which the plate is heated from both the upper and lower sides to assure a uniform heating of the material at a high speed.

The industrial furnace of the present invention em- I By heating the plates from the above and below, they are uniformly heated; The floor burners apply heat directly to the underside of the plates. This is particularly important once relatively large amounts of heat energy are withdrawn from the plate underside through its contact with cooled slide rails and supports. Clogging of the upwardly directed burner nozzles from falling scale is prevented since the burners automatically blow themselves clean. Between adjacent floor burners and the underside of the plate there is a downwardly directed flow which directs scale to and deposits the scale in the area between adjacent burners.

To maintain the burner nozzles free of scale even if a substantial amount of scale has collected between the burners the burner nozzles preferably are elevated above the furnace bottom level on which scale collects.

In a preferred embodiment the burner nozzles are arranged in parallel rows and on continuous banks defined by the furnace floor. A trough is defined between the banks from which the scale is easily removed with scrapers or the like.

Usually transverse support members are provided in the furnace which mount longitudinally extending slide rails upon which the plates or other material moves through the furnace. Preferably, the burner nozzles are aligned with the support members to thereby more effectively maintain a substantially uniform heat and/or heat build-up as the plate moves through the furnace by more evenly supporting the burners flames over the underside of the plate.

To prevent clogging of the inoperative or turned-off floor burners each burner is preferably provided with a free, straight and vertically disposed burner tube or duct that has a radially extending fuel supply conduit adjacent its lower end. The lower end of the tube or duct is connected to a lower scale bag or collector which is closed with a suitable door for periodic cleaning. If scale falls on to the burner it drops through the vertical burner tube for subsequent removal from the scale collector.

The burners are preferably high speed burners which can be regulated from a full-load operating mode at which the heel and/or flame (hereafter gas) is discharged at a speed at least about to meters per second to a throttled operating mode at which the gas is discharged at a speed as little as one-seventh that speed or a minimum gas discharge speed of about 11 meters per second. The burners are preferably free jet burners, that is burners which discharge gases in a substantially uniform stream that spreads into a cone after the gas is released by the burner nozzle. The burner further preferably imparts a swirl or rotating component to the discharged gas. Without such swirl component the discharged gas cone is smaller. With the swirl component the cone is upwardly and outwardly flared. If, therefore, burners having a swirl component are used the overall number of burners can be smaller since each covers a larger area than that covered by a burner discharging the gas without swirl component.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational schematic representation of an industrial furnace; and

FIG. 2 is a side elevational representation of the furnace shown in FIG. 1. Y

DESCRIPTION OF THE PREFERRED EMBODIMENTS The industrial furnace shown in the drawings is a pusher type, slab heating furnace. It is apparent that the furnace can be any other type of industrial furnace as, for example, a lifting hearth furnace. In the heating space 1 of the furnace are a plurality of parallel rows of support members 2 arranged side by side in the transport direction V in which slabs 6 move through the furnace. The supports are cooled with water flowing through suitable cooling pipes 3. Mounted on top of the support members are a plurality of side by side, parallel slide rails which extend in the transport direction V and which are cooled by water flown through cooling pipes 5. The heating space of the furnace has a sufficient width so that two slabs 6 can be simultaneously conveyed through the furnace side by side in the transport direction.

A plurality of downwardly facing upper burners 8 are installed in furnace ceiling 7 and equally distributed over the ceiling area. To simplify the drawings only few upper burners 8 are shown. It will be understood, however, that in actuality they are evenly distributed as above described. The upper burners discharge the gas downwardly against the upper surface of the slab.

A plurality of lower or floor burners 10 are installed in furnace floor and are evenly distributed over the floor as more fully described hereinafter. The floor burners discharge a fuel jet in an upward direction against the underside of slab 6. To simplify the drawing again only a few of the floor burners are illustrated in detail.

The floor burners are arranged in parallel rows on banks 12 which extend perpendicular to the transport direction V and which are vertically aligned with slide rail support members 2. Adjacent banks 12 form between each other troughs 13 in which decending scale collects during operation of the furnace. Scale accumulated in the troughs can be removed from time to time through doors 14 arranged at the ends of the troughs.

Discharge nozzles 23 of the burners are thus elevated above the furnace floor defined by the bottom of troughs 13.

Floor burners 10 include vertically oriented, straight free burners tubes or ducts 15 which define the burner nozzles. The lower end of each tube is attached to a scale bag 17 closed by a door 16. Radially extending fuel gas conduits l8 and 19 connected to burner tube 15 adjacent the lower end thereof and are arranged to impart the above described radial or swirl component to the gas discharged by the burner nozzle.

Since slabs 6 are heated from below by floor burners 10 arranged in furnace floor 9 the slabs are more uniformly and evenly heated than is possible with prior art furnaces employing ceiling burners only. Falling scale does not clog burner tubes 15 since such scale is blown away by the discharged gases during operation of the floor burners. The falling scale is additionally directed for deposit in troughs 13 by the downwardly flowing gas flows 20, 21 produced by the floor burners.

The straight burner tubes 15 effect a fuel gas discharge from burner discharge nozzles 23 at high speed. If, for example, the gases in the lower region of the burner tube have a valocity of say 15 meters per second then the velocity of the gas discharged by the nozzle is substantially increased as a result of the gas combustion and the accompanying increase in the gas volume to as much as about seven times the initial gas speed at the burner tube bottom. This assures that the gas exit velocity is sufficiently high over the entire regulation range of the burner to blow all scale falling from the slabs away from the floor burners and thus prevent the clogging of the burners.

The right hand portion of FIG. 1 shows the gas flow of two free jet burners which have a swirl component 22. To the left thereof are illustrated two free jet floor burners which discharge gas without such swirl component. In each, however, a back flow 20, 21 is formed between the burners which discharge gas without such swirl component. In each, however, a back flow 20, 21 is formed between the burners which allows scale to descend between adjacent burner nozzles and settle in trough 13. The swirl component of the free jet also insures that falling scale is projected radially outward. A considerable part of the scale, therefore does not have to travel upward along the entire path of the free jet. For example, as high as about one-half the vertical distance between the burner nozzle and the plate the scale passes from the ranges of the upwardly directed discharged gas into the back flow 20, 21 from where it settles in trough 13.

We claim:

1. In an industrial furnace having a heating space disposed between a furnace ceiling and a furnace floor and means for conveying scale shedding objects to be heated such as steel slabs horizontally through the furnace at an elevation spaced from both the floor and the ceiling, the improvement comprising a plurality of spaced apart substantially vertically oriented floor burners, each burner having an upwardly facing fuel discharge nozzle for vertically directing fuel towards an underside of the object, and means for supplying each burner when operating in its turned-down mode with gas of sufficient pressure so that the gas discharge speed at the nozzle exceeds the free fall speed of scale descending from the object above the nozzles.

2. An industrial furnace for heating a debris shedding object moving through the furnace along a horizontal path comprising: means for movably supporting the object in a substantially horizontal position between a furnace floor and a furnace ceiling, means for directly heating an upper side of the object as it moves through the furnace, a plurality of floor burners evenly distributed beneath the trabel path of the object, each burner having an upwardly facing nozzle for the discharge of fuel jet towards an underside of the object, the nozzle defining an opening through which the jet escapes in an upward, substantially vertical direction, and means for the discharge of gas by the nozzles at a speed which is greater than the free-fall speed of debris dropping off an underside of the object when the floor burners are in their turned-down operating mode to thereby directly heat the underside and prevent debris from entering and clogging the nozzles and floor burners.

3. A furnace in accordance with claim 2 including means raising the discharge nozzle above the furnace bottom.

4. A furnace according to claim 2 including a plurality of floor burners arranged in parallel rows extending in the direction of movement of the object throughthe object support means includes support members extending perpendicularly to the object transport direction through the furnace, and wherein floor burner nozzles are vertically aligned with the support members.

6. A furnace according to claim 2 wherein each floor burner includes straight burner tube means, a scale collecting container secured to a lower end of the tube means, means for selectively opening the 9al99 2tr ma @n mans o intwqysins a gas flow into the burner tube in a generally radial direction.

A furnace according to claim 2 wherein the floor 

1. In an industrial furnace having a heating space disposed between a furnace ceiling and a furnace floor and means for conveying scale shedding objects to be heated such as steel slabs horizontally through the furnace at an elevation spaced from both the floor and the ceiling, the improvement comprising a plurality of spaced apart substantially vertically oriented floor burners, each burner having an upwardly facing fuel discharge nozzle for vertically directing fuel towards an underside of the object, and means for supplying each burner when operating in its turned-down mode with gas of sufficient pressure so that the gas discharge speed at the nozzle exceeds the free fall speed of scale descending from the object above the nozzles.
 2. An industrial furnace for heating a debris shedding object moving through the furnace along a horizontal path comprising: means for movably supporting the object in a substantially horizontal position between a furnace floor and a furnace ceiling, means for directly heating an upper side of the object as it moves through the furnace, a plurality of floor burners evenly distributed beneath the travel path of the object, each burner having an upwardly facing nozzle for the discharge of fuel jet towards an underside of the object, the nozzle defining an opening through which the jet escapes in an upward, substantially vertical direction, and means for the discharge of gas by the nozzles at a speed which is greater than the free-fall speed of debris dropping off an underside of the object when the floor burners are in their turned-down operating mode to thereby directly heat the underside and prevent debris from entering and clogging the nozzles and floor burners.
 3. A furnace in accordance with claim 2 including means raising the discharge nozzle above the furnace bottom.
 4. A furnace according to claim 2 including a plurality of floor burners arranged in parallel rows extending in the direction of movement of the object through the furnace and on continuous banks elevated above the furnace floor and disposed perpendicularly with respect to the rows.
 5. A furnace according to claim 2 wherein the object support means includes support members extending perpendicularly to the object transport direction through the furnace, and wherein floor burner nozzles are vertically aligned with the support members.
 6. A furnace according to claim 2 wherein each floor burner includes straight burner tube means, a scale collecting container secured to a lower end of the tube means, means for selectively opening the scale collecter means, and means for introducing a gas flow into the burner tube in a generally radial direction.
 7. A furnace according to claim 2 wherein the floor burners comprise high-speed burners having a regulating range of about one to seven between their lowest and highest capacity operating modes, and wherein the jet outlet speed on the uppermost operating mode conditions is at least between about 80 to 100 meters per second.
 8. An industrial furnace according to claim 2 wherein the floor burners comprise free jet burners.
 9. An industrial furnace according to claim 2 wherein the floor burners comprise free jet burners and means for introducing a swirl component into the jets discharged by The nozzles. 